Various metals, and particularly, alloys of aluminum, steel, iron, etc., are commonly used in marine, aerospace, construction, automobile and other applications. Corrosion inhibitive compounds have long been used in an effort to protect these metallic surfaces. Generally, these alloys are protected against corrosion by applying primers or volatile organic coatings containing corrosion inhibitors.
A variety of treatments have been developed in an attempt to provide corrosion resistant properties. Typically, such treatments utilize organic solvents as well as chromium-based compounds. Examples of such compounds include: barium or strontium chromate particles used as inhibitive pigments in adhesives, paints and primers; and chromic acid, which is used to produce a chromium rich conversion coating. Inorganic pigments derived from salts of zinc and chromate (Cr VI) metals have been used in corrosion resistant primer paints on metal surfaces. Alkali earth metal chromates containing trivalent as well as hexavalent chromium as additives for metal protective pigments are disclosed by Patterson, et al., in U.S. Pat. No. 2,387,528 and protective pigments comprising calcium chromate associated with minor additions of ferric, manganic or chromic oxides are described by C. Sloan in U.S. Pat. No. 2,430,589.
Typical corrosion resistant primers used for metals are solvent based epoxy primers which employ hexavalent chromium as an active corrosion inhibitor pigment additive. These primers rely on the hexavalent chromium for corrosion protection. However, chromium conversion coating is the subject of concern due to its toxicity to humans and to the environment. Hexavalent chromium compounds are recognized by the U.S. National Institute of Environmental Health Sciences (NIEHS) (Report on Carcinogens, Eleventh Edition) as a known Group I human carcinogen. With both federal and state legislative efforts to reduce the use of hexavalent chromium and volatile organic content in paints and primers, developing chromium-free, waterborne corrosion resistant compositions is vital.
It is extremely desirable to find a waterborne, chromium-free solution for effective corrosion resistance in the effort to reduce both the emission of Volatile Organic Compounds (“VOCs”) and the use of toxic chromium compounds. The present invention provides water based, organic, chromium free additives, formulations, and primers that provide the desired corrosion inhibition for metals.
It is to be understood that the foregoing is exemplary and explanatory only and are not to be viewed as being restrictive of the invention, as claimed.
It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not to be viewed as being restrictive of the invention, as claimed. Further advantages of this invention will be apparent after a review of the following detailed description of the disclosed embodiments, which are illustrated schematically in the accompanying drawings and in the appended claims.